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We study commutativity of rings R with the property that for each nonperiodic element x of R there exists a positive integer K = K(x) such that xk is central for all k≥K. 相似文献
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Huanyin CHEN Department of Mathematics Hunan Normal University Changsha China. 《数学年刊B辑(英文版)》2007,28(6):617-628
A ring R is a QB-ring provided that aR bR=R with a,b∈R implies that there exists a y∈R such that a by∈R_q~(-1).It is said that a ring R is a JB-ring provided that R/J(R)is a QB-ring,where J(R)is the Jacobson radical of R.In this paper,various necessary and sufficient conditions,under which a ring is a JB-ring,are established.It is proved that JB-rings can be characterized by pseudo-similarity.Furthermore,the author proves that R is a JB-ring iff so is R/J(R)~2. 相似文献
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The notion of cross-bandwidth is introduced, and it is shown that any graph that is suitably contractible to a k-connected graph has cross-bandwidth at least k. The contracted edges must induce in the original graph a subgraph of maximum degree at most one. This is used to resolve a conjecture of Erdös and Chinn on the bandwidth of certain graphs. 相似文献
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Grigor Sargsyan 《Archive for Mathematical Logic》2008,47(7-8):765-768
During his Fall 2005 set theory seminar, Woodin asked whether V-supercompactness implies HOD-supercompactness. We show, as he predicted, that that the answer is no. 相似文献
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In this paper we introduce semi-pseudo-ovoids, as generalizations of the semi-ovals and semi-ovoids. Examples of these objects are particular classes of SPG-reguli and some classes of m-systems of polar spaces. As an application it is proved that the axioms of pseudo-ovoid O(n,2n,q) in PG(4n−1,q) can be considerably weakened and further a useful and elegant characterization of SPG-reguli with the polar property is given.Research Assistant of the Fund for Scientific Research Flanders (FWO-Vlaanderen) 相似文献
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In this paper, we study the class of rings in which every flat ideal is finitely generated. We investigate the stability of this property under localization and homomorphic image, and its transfer to various contexts of constructions such as direct products, pullback rings, and trivial ring extensions. Our results generate examples which enrich the current literature with new and original families of non-Noetherian rings that satisfy this property. 相似文献
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In this article a unified approach is presented to hypertopologies on collections of nonempty closed subsets of a Hausdorff uniform space generated by a saturated and separating family of pseudo-metrics. One identifies here a suitable topology on the family of proper, convex and lower semicontinuous functions defined on a Hausdorff locally convex space for which the Young Fenchel transform is bicontinuous. This improves a well known result due to Mosco, Joly and Beer. 相似文献
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W. K. Nicholson 《Periodica Mathematica Hungarica》1993,27(2):85-88
A ringR is called a leftPP-ring if every principal left ideal is projective, equivalently if the left annihilatorl(a) is generated by an idempotent for allaR. These rings seem first to have been discussed by Hattori [2] and examples include (von Neumann) regular rings and domains (possibly noncommutative). In this note we give a new characterization of leftPP-rings, use that to give an elementary proof of a result of Xue [4] characterizing triangularPP-rings, and then determine when the ringT
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(R) of upper triangular matrices overR is a leftPP-ring. Throughout the paper all rings have a unity and all modules are unitary.This research was supported by NSERC Grant A8075 相似文献
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本文主要利用分段连续的Lyapunov函数得到脉冲比较微分系统(2)的φ0-稳定性,并且通过比较方程,得到脉冲微分系统(1)的稳定性. 相似文献
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Christoph Bandt 《Mathematische Nachrichten》1977,77(1):333-351
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